全文获取类型
收费全文 | 22498篇 |
免费 | 1218篇 |
国内免费 | 2645篇 |
专业分类
林业 | 2271篇 |
农学 | 1886篇 |
基础科学 | 2986篇 |
4716篇 | |
综合类 | 9830篇 |
农作物 | 786篇 |
水产渔业 | 913篇 |
畜牧兽医 | 1508篇 |
园艺 | 326篇 |
植物保护 | 1139篇 |
出版年
2024年 | 294篇 |
2023年 | 644篇 |
2022年 | 921篇 |
2021年 | 851篇 |
2020年 | 919篇 |
2019年 | 1011篇 |
2018年 | 686篇 |
2017年 | 1025篇 |
2016年 | 1228篇 |
2015年 | 1100篇 |
2014年 | 1166篇 |
2013年 | 1274篇 |
2012年 | 1628篇 |
2011年 | 1674篇 |
2010年 | 1380篇 |
2009年 | 1293篇 |
2008年 | 1221篇 |
2007年 | 1284篇 |
2006年 | 1096篇 |
2005年 | 915篇 |
2004年 | 717篇 |
2003年 | 584篇 |
2002年 | 462篇 |
2001年 | 354篇 |
2000年 | 335篇 |
1999年 | 308篇 |
1998年 | 276篇 |
1997年 | 272篇 |
1996年 | 234篇 |
1995年 | 231篇 |
1994年 | 187篇 |
1993年 | 164篇 |
1992年 | 157篇 |
1991年 | 146篇 |
1990年 | 122篇 |
1989年 | 91篇 |
1988年 | 63篇 |
1987年 | 22篇 |
1986年 | 8篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1982年 | 1篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1963年 | 2篇 |
1962年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
This article presents an implement of component using COM technology for collecting environmental monitoring data in environment monitoring system. The component makes the separation of data collection and data analysis available.Simultaneously by using the interface of connectable object in COM,itmakes the cooperation of the environment monitoring software with other parts of fault management software available,and also the seamless connection.It improves the system's performance by adding extensibility and potential cooperatibility. 相似文献
72.
REN Guang-sheng 《保鲜与加工》2001,(3):22-25
Characteristics of a tire are the foundation of vehicle dynamics studying, especially play a vital role in vehicle handling study. It is necessary to establish a tire model in the simulation for vehicle handling because the tire characteristics got by test can not be satisfied.The optimization of fitting to the tire test data curves by Magic Formula is discussed, included the digitalization of tire test data curves, designing objective functions and optimization processes,etc. Finally the parameters in Magic Formula tire model are obtained and they lay a foundation for the development of vehicle handling aftertime. 相似文献
73.
Tu Yaqing Huang Shanglian Li Zushu 《保鲜与加工》1993,(6):8-15
Based on the model of Human Simulation Intelligent Controller (HSIC)
presented briefly, a detailed algorithm was described for the servo system control by using the method of HSIC. Simulation results obtained proves the good performance of the control algorithm. 相似文献
74.
With the development of circulating fluidized bed boiler(CFB),the study field of external heat exchanger(EHE) is greater in extent and degree.In order to research the working process of EHE,the model which deals with flow and heat transfer of EHE for 300MW CFB of Dong Fang Boiler Grou PCo.Ltd.is presented.Based on the cell modeling theory,the EHE is divided into several chamber by heating surfaces.The mass and energy conservation equations of each cell have been developed according to some reasonable assumption.The complete mathematical model has been compiled by Fortran and solved by classical Algorithm of Runge-Kutta.The static test and perturbation experiment of simulating model has been performed.The simulation results show that the model has been reached the steady state rapidly,the dynamic responses are reasonable and the modeling presented in the paper is reliable and appropriate. 相似文献
75.
76.
ZHAN Xue-gang 《保鲜与加工》2005,(6):139-142
This article briefly introduces the principle and the character of the leverage buyouts since the rate of finance lever and the risk is high in the LBO, this article gives a game-theory analysis on the financing process between the purchaser and the investor in LBO by using the ROSS model. It is expected that some beneficial proposal to either side can be put forward by parting the equilibrium.in the last, it poses that LBO can be a way of broadening the financing channel on the annexation between the enterprises in our country. 相似文献
77.
This paper introduces the modeling of Unified Modeling Language with use case diagram and active diagram based on Rational Unified Process for Equipment Managemet Information System. It discusses the modeling mechanism and character of UML and develops the Computer Equipment management Information System Based Web using Rational Rose of UML CASE Tool. First, it is describe the authors how to analyze the structure of organize and build the model of structure organize. Second, they abstract the workflow of main operation in organize and build workflow model by active diagram. Finally, they abstract actor, use case with case diagram and finish the requirement model. 相似文献
78.
Tu Zhiying Yu Chuzhong 《保鲜与加工》1988,(1)
In this paper, the machine( physical) parameters of the alternator system are on-line estimated on the basis of the derived system continuous-tims model, using Recursive Least-squares Estimation and Inverse Calculation Method proposed by Authors. Therefore, the estimated machine parameters can effectively track the changes of their true values and accomplish the fault detection for the alternator system. This paper gives a new way for machne parameter estimation and fault detection of the alternator systems. 相似文献
79.
CHEN Yao-hui~ 《保鲜与加工》2004,(8):86-91
We prove a Donsker type approximation theorem for the fractional Brownian motion in the case of the Hurst index greater than one half. With this approximation we construct an elementary market model that converges weakly to the fractional analogue of the Black Scholes model. We show that there exist arbitrage opportunities in this model. 相似文献
80.